1. Technical Field
Embodiments of the present invention relate to an electrophoretic display apparatus and an operating method thereof. More particularly, embodiments of the present invention relate to an electrophoretic display apparatus capable of displaying a plurality of images on one screen and a method of operating the electrophoretic display apparatus.
2. Description of the Related Art
Electrophoretic display apparatuses have been extensively used in various electronic devices such as a portable electronic dictionary, a portable mobile product and so on. Generally, the electrophoretic display apparatus includes a display panel and a driver. The display panel includes two substrates facing each other and an electrophoretic layer interposed between the two substrates. The two substrates are provided with first and second electrodes, respectively. The electrophoretic layer includes charged particles moving between the first and second electrodes due to a potential difference formed between the first and second electrodes. The driver applies voltage pulses in the form of direct current (DC) corresponding to an image to one of the first and second electrodes, so that the potential difference occurs between the first and second electrodes. If the potential difference occurs between the first and second electrodes, the particles are aligned in a predetermined position between the first and second electrodes. A predetermined image is displayed according to the alignment state of the particles. Such an electrophoretic display apparatus continuously displays an image corresponding to the voltage pulses even if the voltage pulses are not supplied to the display panel. Accordingly, the electrophoretic display apparatus continuously displays a predetermined image with low power consumption.
Meanwhile, the electrophoretic display apparatus employs a driving scheme different from a driving scheme of a conventional display apparatus (e.g., a liquid crystal display) because the electrophoretic display apparatus uses charged particles. For example, if the voltage pulses are not applied to the display panel for a long time, the image corresponding to the voltage pulses loses an intrinsic gray scale level. This is because the particles move from a predetermined position corresponding to the intrinsic gray scale level to another position due to several causes. Accordingly, the electrophoretic display apparatus requires an additional voltage periodically applied to the display panel in order to maintain the intrinsic gray scale level. In other words, the additional voltage is applied to the display panel at a time point when a user senses the degradation of an image.
In the electrophoretic display apparatus, if voltage pulses having the same polarity are continuously applied to a pixel during plural previous frames, a predetermined amount of charges are continuously accumulated in the pixel, and the accumulated charges exert a bad influence on a voltage pulse applied to a present frame. Accordingly, the electrophoretic display apparatus performs direct current balancing to apply a voltage pulse having a polarity opposite to a polarity of a voltage pulse during previous frames to the pixel, thereby removing charges accumulated in the pixel.
Conventionally, when a plurality of images are sequentially displayed on one screen, an additional voltage is simultaneously applied to the images at a predetermined time point regardless of the sequence of the displayed images. Accordingly, the additional voltage is applied in relation to remaining images except for an image that has been displayed in the first stage, even though the gray scale of the remaining images is not actually degraded. Thus, pixels displaying the remaining images are over-charged, so that DC balancing of the voltage pulses applied to the pixels is not adjusted.